Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 190211
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1011 PM EDT Wed Apr 18 2018

.SYNOPSIS...
Low pressure system will track east over the Ohio Valley this
evening and into the northeastern states pushing a cold front
across our region early on Thursday. High pressure will build on
Friday and remain in control into the weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
Clear to mostly clear skies continue over our area, with some
clouds over our higher elevations in the northwest and across
parts of central Maryland near the Mason-Dixon line.

A warm front is expected to lift overnight with clouds increasing
over us. At the same time, a low pressure system will approach
from the west which is expected to increase showers over our
CWA, but mainly to the Allegheny Highlands. ECMWF brings chance
PoPs east of the Blue Ridge, while most other guidance is drier.
Therefore, expecting precipitation mainly over areas west and
near the Mason-Dixon Line, but not ruling out some showers over
the rest of our area.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
Low pressure will be tracking towards the northeastern states
on Thursday as it pushes a cold front over us. Some showers are
possible on Thursday as an upper trough axis moves overhead.

Gusty northwesterly winds are expected behind the front as cold air
advects over us and a dry air mass settles in. Winds gusts between
30 and 40 mph expected, with higher gusts at the ridge tops. A
Wind Advisory has been issued for ridges above 2,000 ft from
midnight tonight through Thursday for wind gusts greater than
45 mph. An expansion of this advisory to other areas will be
evaluated by upcoming shifts (lower confidence at lower
elevations since the best gradient/pressure surge pushes east
prior to favorable diurnal mixing). Cold air advection behind
the front will allow for snow showers west of the Allegheny
Front Thursday afternoon and evening. Expecting accumulations
between a coating to an inch or two.

A Canadian high pressure center will from the northwest on
Friday. Gusty winds will be gradually decreasing through the day
and finally subsiding by Friday evening. Some clouds may remain
through the day with upper troughing linger, but should be
clearing Friday evening into the night.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
High pressure centered over the Great Lakes will build in for the
weekend, maintaining cool and dry conditions over the area. Winds
will weaken and shift from light northerly to light easterly as high
pressure slides off to our north.

By Sunday Night, models have a cutoff upper-level low and
associated surface low tracking through the Deep South. Over the
past day, models had trended weaker with a positively tilted,
southeastward translating shortwave trough located over the
northeast. Now it appears as though the area of low pressure
associated with the cutoff upper-level trough will slowly track
up the eastern seaboard (as opposed to being suppressed to the
south and pushed out to sea as in previous runs). There are many
complex moving parts, so forecast confidence is low at this
point. However, ensembles and deterministic guidance suggest
that rain could be possible at some point in the late Monday
through Tuesday time frame, along with cool temperatures.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
VFR expected through Thursday night. BKN-OVC conditions through
Thursday as low pressure passes to the north. This low will
drag a cold front through early Thursday, with strong W flow
20-30 G 35+ kts in its wake.

VFR conditions Friday through Monday. Breezy NW flow 10-20 G 25
kts Friday diminishes by Friday evening and remains light through
the weekend.

&&

.MARINE...
SE SCA gusts expected tonight over middle MD Chesapeake
Bay/lower tidal Potomac. Gale Warning for all waters Thursday
with blustery W flow. Gale Warning continues for MD Chesapeake
Bay waters Thursday night with SCA elsewhere as winds gradually
subside. SCA may need to be extended into Friday.

Pleasant boating conditions are expected through the weekend
with high pressure overhead and light winds.

&&

.FIRE WEATHER...
Drier air advecting into the region Thursday on gusty west winds
could result in an enhanced risk of fire spread Thursday.

&&

.TIDES/COASTAL FLOODING...
Water levels will remain elevated through Thursday at the DC
southwest Waterfront, but flooding is not anticipated.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Wind Advisory until 6 PM EDT Thursday for MDZ501.
VA...Wind Advisory until 6 PM EDT Thursday for VAZ503-504-507-508.
WV...Wind Advisory until 6 PM EDT Thursday for WVZ501-503-505-506.
MARINE...Gale Warning from 6 AM Thursday to 6 AM EDT Friday for
     ANZ530>534-538>541-543.
     Small Craft Advisory until 6 AM EDT Thursday for ANZ533-534-
     537-542-543.
     Small Craft Advisory from 6 PM Thursday to 6 AM EDT Friday for
     ANZ535>537-542.
     Gale Warning from 6 AM to 6 PM EDT Thursday for ANZ535>537-542.

&&

$$
SYNOPSIS...KLW
NEAR TERM...KLW
SHORT TERM...KLW
LONG TERM...JMG
AVIATION...KLW/JMG
MARINE...KLW/JMG
FIRE WEATHER...KLW
TIDES/COASTAL FLOODING...KLW



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